Rain is falling vertically downwards with a speed of 4 km `h^(-1)` . A girl moves on a straight road with a velocity of 3 km `h^(-1)` . The apparent velocity of rain with respect to the girl is :

Options

A. 3 km `h^(-1)`
B. 4 km `h^(-1)`
C. 5 km `h^(-1)`
D. 7 km `h^(-1)`

Answer

C

Explanation

`vec(V_(rg))=vec(V_(r))-vec(V_(g))=vec(V_(r)) + (-vec(V_(g)))`
`:.|vec(V_(rg))=sqrt(V_(r)^(2) + V_(g)^(2))`
`=sqrt(16 +9)`
5km/h